Treating storage-battery plates



Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE WILLIAM SCOTT HUTOHIN'SON, OI SOABSDALE, NEW YORK, ASSIGNOB, BY HESNE A8- SIGNMENTS, TO LEK'IOPHONE CORPORATION, OF JERSEY CITY, NEW JERSEY, A

conrom'rr'on or nnnawann rename STORAGE-BATTERY PLATES No Drawing.

This invention relates to the treatment ofstorage battery plates of the pasted or Faur type whereby the expense and labor of the manufacture of such plates are greatly re- 5 duced.

It has been the usual practice in making such plates to form a mix or paste of lead oxide or lead oxides or of such oxide or oxides and lead sulphate to which is added sulphuric acid of considerably less specific gravity than that employed as the elctrolyte in the operation of the battery in normal use. This mix is then pasted on the grid. The pasted grids or plates are then pickled by immersion in comparatively dilute sulphuric acid, usually about 1100 specific gravity. The plates either singly or assembled in groups as may be desired to form the elements, that is the anode and cathode, of a battery and are then formed (convertin the paste into lead peroxide and spongy lea in the positive and negative plates respectively by the electric current, the positive element being made the anode) in a solution of dilute acid, say about 1100 specific gravity. When formation is complete, the elements are immersed in their jars or containers, the electrolyte being'sulphuric acid usually of a specific gravity of 1300, and the battery is continued in its normal use in this electrolyte. The use of two acid solutions as referred to above, is costly and calls for several operations;

The main object-of the present invention is to reduce the labor and cost. This is accomplished by using but one acid solution in treating the plates as compared with a number of acid solutions as noted above. This result may be brought about by treating the pasted plates in acid solutions of such specific gravity and so constitutingthe paste or active material that the acid liberated from the paste during the treatment vwill increase the specific avity to the value desired in the electrolyte or normal operation of the cell.

This may be done by causing the paste containing the usual lead oxides to have a high sulphate content. To accomplish this sulphuric acid of a higher specific gravity than that ordinarily used may be employed in the mix and this forms sulphate which, when de- Application filed october. 27,1925. Serial 110.85.248.

sulphation takes place, gives up acid to the electrolyte or acid solution and thereby raises its specific avity. The roportions of ingredlents w ereby the rig t amount of acid thus given up from the paste to the soluacid may be employed and avery finely divided lead sulphate added. A sulphate suitable for this purpose is such as is made by the process as described in the Patent No. 1,524,314 John A. Schaefer, John H. Caldbeck and Bernard S. White, patented J anuary 27, 1925. Such lead sulphate is readily desulphated when it receives the current.

The desired sulphate in the paste may also be produced by both adding high gravity acid and finely divided sulphate in suitable amounts.

When the sulphate is obtained in the mix, either b using the high gravity acid in the mix or liy using the dry finely divided lead sulphate, or both, which is carefully calculated from the standpoint of producing a certain amount of sulphuric acid when it is desulphated. In this way it is possible to start with an electrolyte or acid of a definite strength or specific gravity and know that when the sulphate in the paste is desulphated an additional amount of sulphuric acid will be produced and raise the specific gravity of the electrolyte by such desulphation, to any given point depending upon the amoun'tof sulphate that is in or is producedin the plate and which is under control by putting a measured amount of acid or a given weight of lead sulphate, or both, in the mix.

Heretofore it was not practicable to employ an acid solution of as high specific gravity 7 as is contemplated in. the present process.

percentage of litharge,are immersed in sulphuric acid, especially acid high in gravity (and particularly the more reactive thelitharge or oxide of lead) lead sulphate is formed immediately. The formation of the lead sulphate causes a great, expansion in volumetending to close the pores and to prevent diffusion to the interior of the plate.

. Inasmuch as the surface of the plate is first attacked by the acid the lead sulphate there formed tends to create a skin or membrane of small thickness and of such density as to shut off the acid from the interior of the plate and when, in the usual procedure, formation is proceeded with in such high gravity acid, the formation of the plate is substantially limited to the small thickness of the skin or 3 f membrane. The result is low capacity and gravity acid.

the practical failure of formation in high By the'present process the prevention of incomplete formation in high gravity acid is avoided by intermittently applying electric current, current being applied as in the ordinary development of plates but intermittently. The action then is, as I understand it, that the sulphate formed on the plate at plate is complete.

' gravity acid is avoided, and the closing of t the surface during the period of no current flow whereby the sulphate barrier tothe dif- $0 Also it may be observed that the successful operation of the present process of treat-1 ment in high gravity acid as herein set forth, is believed to be largely due to the formation of the sulphate in the paste before it is applied to the grid so that the usual expansion (whereby the pores are practically closed and the membrane formed) in the formationv of the sulphate on immersion in higlh e pores therefor proceeds to a much more limited extent so that the diffusion of the acid into the paste is much less interfered with.

The action seems to be aided if the condition is such thatthere ismaintained-a small percentage of the peroxide of lead (which is. in contact with the acidin the paste) and which isdifl'used throughout the paste so that the membrane or impervious layer of sulphate is not complete buthas intermixed init crystals of lead peroxide which'maintain porosity to a limited extent so that during'the periods at which current is appliedthe solution can penetrate to a sufiicient extent to effect the operations as above 1nd1- cated. 1

plates may mixer. To this mixture is added,and thoroughly mixed therein, 120 grams of water so:

as to moisten the oxide, and then 313 cubic centimeters ofsulphuric acid of specific gravity of 1250 is very slowl added with steady mixing of the material. This produces a mass of paste of the desired plasticity which is then pasted on a suitable grid (for instance the standard starter grid which is about of an inch thick), and the pasted grid is then dried.

The negative plates may be made as follows In this case the material may be the same ,as in the case of the positive plates, namely litharge.90% and red lead 10% towhich 10% of the superfine lead sulphate'has been added, the red leadand litharge amounting 'to 2200 grams. The mixing, however, is proceeded with according to the common practice namely, mixing with the aforesaid material sulphuric acid of 1100 specific gravity, the materials being thoroughly mixed. This is pasted on.a grid which may be the regular standing grid "3 g of an inch thick and the whole is then dried. i v

A seven plate cell may then be madeup bytaking four of the dried untreated pasted negative plates and three of the dried positive untreated pasted plates, prepared as above, and grouping them into the desired elements in the'usual way, with the separators, and placing them inth'e regular standard jar for thatnumber 'of plates, which will hold about 600 cubic centimeters of solution, and the jar is filled with sulphuric acid solution of specific gravity 1240. The

cell is then sealed in the regular way andis ready for the current treatment. Current is then applied at the rate of Gamperes-for a periodof five hours, current is then turned off for a succeeding period of three hours, the current is then applied for a succeeding period of three hours, current is then turned off for a succeeding period'of four hours,

current is again applied for a succeeding period of eight hours and turned ofi for a sue: ceeding period of four hours when the current was again turned on-until the treatment was completed which occurredv within four and one-half hours, the specific gravity of the acid solution then being 1280. The usual discharge is then taken and on recharge the solution reached a specific gravity of 1290 which is appropriate for the battery duringnormal use. Y

65 As a concrete illustration of the applica- It willthus be seen thatb y process the cific gravity.

sulphuric acid up to its normal operating strength.

In testimony whereof I have signed this specification this 26th day of October, 1925. WILLIAMSCOTT HUTCHINSON..

bled in the untreated pasted condition in the container with the one acid solution.

A convenient index for the periods of application of current and cessation of current in the treatment of the plates although such index need not be strictly followed, is formed in the change of specific gravity of the solution. During a period of cessation of current sulphation takes place with consequent absorption of acid and lowering of specific V gravit of the solution. When it is observed that t e specific gravity does not substantially lower upon continuation of current cessation, the sulphation has reached its approximate limit and further continuation of the. cessation period is futile. The current should nowfbe applied and, resulting in desulphation, causes acid to be liberated which passes into the solution and raises its spe- This continues until the desulphation has proceeded to its limit when the specific gravity of the solution will no longer substantially rise and it is then appropriate to discontinue the period of current flow and cause a cessation of current for a period such that the specific, gravity of the solution no longer substantially lowers when the current should be a ain applied and continued until the spec c gravity no longer substantially rises and so' that periods of cessation and application are alternated until the treatment of the plate is complete.

While the invention has been set forth by means of a concrete example of its application and also the reasons for its operation and its principal features have been set forthto the best of applicantsunderstanding, it is to be understood that the invention is not limited to the details of the process recited or to the reasons or theo of its operation as such details may be wi ely varied without departing from thespirit of the invention and there may be other reasons for the op- V eration than those set forth.

What I claim is: V

The method of manufacturing storage battery cells which comprises applying to the plate grids a paste which contains prior to its application to the grids an oxide of lead I and lead sulphate, forming the plates in a service container by placing them in'the contain'er with sulphuric acid having a specific gravity of at least 1.2 and passing an electric current through the plates, the amounts of the in to the specific gravity of the sulphuric acid dients'in the paste when applied to the grids being so calculated with respect 

